The present invention relates to a method and apparatus for splicing a fresh web to a running web. More particularly, the invention relates to improvements in a method and apparatus for making a splice between running and fresh webs by means of a uniting band which is adhesive at both sides thereof. Still more particularly, the invention relates to improvements in a method and apparatus which can be utilized with advantage for splicing running and fresh webs of relatively low tensile strength. Typical examples of such commodities are webs of cigarette paper or other strip-shaped material which is used in connection with the manufacture and/or processing of smokers' products including plain or filter tipped cigarettes, cigars or cigarillos, filter rod sections and packages and/or cartons for cigarettes or the like.
It is already known to employ a uniting band for the splicing of the leader of a fresh web to the running web, and it is also known to initiate the splicing operation in response to exhaustion or near exhaustion of the supply of running web. The supply of the running web is monitored and the fresh web is accelerated to a speed which is at least slightly less than the speed of the running web before the webs are caused to contact the respective adhesive-coated sides of a uniting band therebetween. Thus, the fresh web invariably undergoes abrupt additional acceleration as soon as it comes in contact with the uniting band or as soon as the uniting band comes in contact with the running web, depending upon whether the uniting band is contacted by the fresh web subsequent or prior to contacting the running web. Such mode of splicing presents no problems when the material of the webs exhibits a pronounced tensile strength, i.e., when the fresh web and/or the running web is not likely to break in response to abrupt acceleration of the fresh web to the exact speed of the running web. For example, a web of metallic foil, paper or lightweight cardboard which is used for the making of inner or outer envelopes of cigarette packs can stand rather pronounced tensional stresses. However, the tensile strength of cigarette paper is very low. Furthermore, the trend in the cigarette making is toward the use of highly porous cigarette paper whose tensile strength is extremely low. In fact, many manufacturers of cigarettes demand that the permeability of highly porous cigarette paper be reduced still further, for example, by making holes with the help of needles, one or more laser beams and/or electrodes which combust portions of a running web at regular intervals. Increased permeability of cigarette paper webs, e.g., in the region of mouthpieces of filter cigarettes, is considered to be desirable in order to allow relatively large amounts of atmospheric air to enter the column of smoke flowing into the smoker's mouth. The admixed atmospheric air is believed to facilitate regulation of the percentage of nicotine and condensates which are inhaled by the smoker.
The problems which arise in connection with automatic or semiautomatic splicing of fresh webs of highly porous cigarette paper to running webs are further aggravated by continuous increase in the output of cigarette making and like machines. Thus, the likelihood of breaking a highly porous cigarette paper web whose tensile strength is extremely low is further enhanced if the web is to travel at a speed which is necessary to turn out up to and well in excess of seventy cigarettes per second.
Acceleration of a fresh web to a speed which is less than the speed of the running web was considered to be not only advisable but actually necessary because such mode of splicing allows for convenient separation of surplus of the leader of a fresh web from that portion of the fresh web which is attached to the running web. All that is necessary is to place a stationary knife into the path of movement of the fresh web ahead of the uniting band. When the fresh web undergoes abrupt acceleration as a result of splicing to the running web, the slowly moving surplus is moved against and is severed by the stationary knife.